1 // SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0 2 /****************************************************************************** 3 * 4 * Module Name: utcksum - Support generating table checksums 5 * 6 * Copyright (C) 2000 - 2022, Intel Corp. 7 * 8 *****************************************************************************/ 9 10 #include <acpi/acpi.h> 11 #include "accommon.h" 12 #include "acutils.h" 13 14 /* This module used for application-level code only */ 15 16 #define _COMPONENT ACPI_CA_DISASSEMBLER 17 ACPI_MODULE_NAME("utcksum") 18 19 /******************************************************************************* 20 * 21 * FUNCTION: acpi_ut_verify_checksum 22 * 23 * PARAMETERS: table - ACPI table to verify 24 * length - Length of entire table 25 * 26 * RETURN: Status 27 * 28 * DESCRIPTION: Verifies that the table checksums to zero. Optionally returns 29 * exception on bad checksum. 30 * Note: We don't have to check for a CDAT here, since CDAT is 31 * not in the RSDT/XSDT, and the CDAT table is never installed 32 * via ACPICA. 33 * 34 ******************************************************************************/ 35 acpi_status acpi_ut_verify_checksum(struct acpi_table_header *table, u32 length) 36 { 37 u8 checksum; 38 39 /* 40 * FACS/S3PT: 41 * They are the odd tables, have no standard ACPI header and no checksum 42 */ 43 if (ACPI_COMPARE_NAMESEG(table->signature, ACPI_SIG_S3PT) || 44 ACPI_COMPARE_NAMESEG(table->signature, ACPI_SIG_FACS)) { 45 return (AE_OK); 46 } 47 48 /* Compute the checksum on the table */ 49 50 length = table->length; 51 checksum = 52 acpi_ut_generate_checksum(ACPI_CAST_PTR(u8, table), length, 53 table->checksum); 54 55 /* Computed checksum matches table? */ 56 57 if (checksum != table->checksum) { 58 ACPI_BIOS_WARNING((AE_INFO, 59 "Incorrect checksum in table [%4.4s] - 0x%2.2X, " 60 "should be 0x%2.2X", 61 table->signature, table->checksum, 62 table->checksum - checksum)); 63 64 #if (ACPI_CHECKSUM_ABORT) 65 return (AE_BAD_CHECKSUM); 66 #endif 67 } 68 69 return (AE_OK); 70 } 71 72 /******************************************************************************* 73 * 74 * FUNCTION: acpi_ut_verify_cdat_checksum 75 * 76 * PARAMETERS: table - CDAT ACPI table to verify 77 * length - Length of entire table 78 * 79 * RETURN: Status 80 * 81 * DESCRIPTION: Verifies that the CDAT table checksums to zero. Optionally 82 * returns an exception on bad checksum. 83 * 84 ******************************************************************************/ 85 86 acpi_status 87 acpi_ut_verify_cdat_checksum(struct acpi_table_cdat *cdat_table, u32 length) 88 { 89 u8 checksum; 90 91 /* Compute the checksum on the table */ 92 93 checksum = acpi_ut_generate_checksum(ACPI_CAST_PTR(u8, cdat_table), 94 cdat_table->length, 95 cdat_table->checksum); 96 97 /* Computed checksum matches table? */ 98 99 if (checksum != cdat_table->checksum) { 100 ACPI_BIOS_WARNING((AE_INFO, 101 "Incorrect checksum in table [%4.4s] - 0x%2.2X, " 102 "should be 0x%2.2X", 103 acpi_gbl_CDAT, cdat_table->checksum, 104 checksum)); 105 106 #if (ACPI_CHECKSUM_ABORT) 107 return (AE_BAD_CHECKSUM); 108 #endif 109 } 110 111 cdat_table->checksum = checksum; 112 return (AE_OK); 113 } 114 115 /******************************************************************************* 116 * 117 * FUNCTION: acpi_ut_generate_checksum 118 * 119 * PARAMETERS: table - Pointer to table to be checksummed 120 * length - Length of the table 121 * original_checksum - Value of the checksum field 122 * 123 * RETURN: 8 bit checksum of buffer 124 * 125 * DESCRIPTION: Computes an 8 bit checksum of the table. 126 * 127 ******************************************************************************/ 128 129 u8 acpi_ut_generate_checksum(void *table, u32 length, u8 original_checksum) 130 { 131 u8 checksum; 132 133 /* Sum the entire table as-is */ 134 135 checksum = acpi_ut_checksum((u8 *)table, length); 136 137 /* Subtract off the existing checksum value in the table */ 138 139 checksum = (u8)(checksum - original_checksum); 140 141 /* Compute and return the final checksum */ 142 143 checksum = (u8)(0 - checksum); 144 return (checksum); 145 } 146 147 /******************************************************************************* 148 * 149 * FUNCTION: acpi_ut_checksum 150 * 151 * PARAMETERS: buffer - Pointer to memory region to be checked 152 * length - Length of this memory region 153 * 154 * RETURN: Checksum (u8) 155 * 156 * DESCRIPTION: Calculates circular checksum of memory region. 157 * 158 ******************************************************************************/ 159 160 u8 acpi_ut_checksum(u8 *buffer, u32 length) 161 { 162 u8 sum = 0; 163 u8 *end = buffer + length; 164 165 while (buffer < end) { 166 sum = (u8)(sum + *(buffer++)); 167 } 168 169 return (sum); 170 } 171